1. Field of the Invention
The present invention relates to a reamer apparatus for a ground boring machine.
2. Description of the Related Art
A pipe burying method for burying a pipe such as a water pipe, a gas pipe, a drain pipe, a sheath pipe for a signal cable, and a fiber cable or the like (hereinafter, referred to as “a buried pipe”) in the earth is roughly divided into a drive construction method for driving the earth and burying a pipe, and a non-drive construction method for burying a pipe without driving the earth. The both construction methods have an advantage and a disadvantage, respectively. In other words, as compared to the drive construction method, the non-drive construction method has an economical advantage such that a pipe can be easily buried as crossing under an orbit of a railroad and a river or the like and a pipe can be buried while preserving the environment, and further, the non-drive construction method is a short construction schedule. Further, according to the drive construction method, a so-called power shovel or the like is used; however, according to the non-drive construction method, a horizontal drill is used. This horizontal drill has a two process system including a pilot excavation, enlargement of a diameter, and retracting a buried pipe, and the present invention relates to a reamer apparatus which is used for a ground boring machine to be used in this two process system.
In the case of burying a buried pipe with a horizontal drill construction, as shown in FIG. 9, at first, a penetration pit P1, a starting pit P2, and an attainment pit P3 are formed on the earth at certain intervals each other. In the vicinity of the penetration pit P1, a drilling fluid feeder 101 and a drill driving device 102 (constructing a horizontal drill) are disposed. Then, a buried pipe 104 is disposed in the vicinity of the attainment pit P3, of which length approximately equivalents to a distance from the starting pit P2 to the attainment pit P3. This is a preparation operation. In the meantime, the drill driving device 102 is defined to be freely promote in the earth as adding a plurality of hollow rods 105, and further, on the contrary, the drill driving device 102 is defined to be freely pulled out from the earth as adding a plurality of hollow rods 105. The drilling fluid feeder 101 stores a drilling fluid such as a crystal water, a muddy water, a bentonite muddy water or the like therein and at the same time, the drilling fluid feeder 101 can freely pressure feed the stored drilling fluid into a hollow of the hollow rod 105 which is disposed on the drill driving device 102 via a hose 107.
Therefore, on the drill driving device 102, the first hollow rod 105 is installed to be supported. At a front end of this hollow rod 105, for example, a leading body (a pilot head) 105a with an outer diameter of about 70 to 100 mm is fit in advance. In the meantime, for example, an outer diameter of the hollow rod 105 is about 40 to 50 mm. Then, by means of the drill driving device 102, the first hollow rod 105 penetrates through the penetration pit P1 obliquely at a penetration angle β (nearly equal to 15°) if the earth is approximately horizontal; the first hollow rod 105 is promoted in an arrow direction A1 toward the starting pit P2 without no rotation while rotating the hollow rod 105; and bending it horizontally, a pilot hole 108 is formed in the starting pit P2. Further, as adding the hollow rods 105 to the attainment pit P3 via the starting pit P2, the hollow rods 105 are promoted in the earth in an arrow direction A2.
In other words, in the case of drilling and making a linear hole, while rotating the oblique leading body 105a that is fit to this rod front end by means of a rotational motor 130 of the drill driving device 102 via the rod 105, the rotational motor 130 is promoted along a frame 131. In addition, in the case of changing a direction (in the case of drilling and making a curved hole), the rotational motor 130 is not rotated but stopped, and under this state, the rotational motor 130 is promoted along the frame 131 (the rod 105 is promoted). Then, making an obliquely-cut surface of the oblique leading body 105a to act on the earth pressure, the direction of the oblique leading body 105a is changed to the opposite direction of the oblique-cut surface to be promoted. Thus, by promoting the rod 105, the curved hole is drilled so that the oblique leading body 105a attains to the attainment pit P3. In the meantime, the pilot head 105a has a plurality of nozzle holes (illustration thereof is omitted) communicating through the hollow of the hollow rod 105. Therefore, upon promoting the pilot head, the drilling fluid that is pressure-fed from the drilling fluid feeder 101 is emitted backward so as to discharge the drilling fluid and the drilled earth and sand backward.
Then, when the leading body (the pilot head) 105a protrudes in the attainment pit P3, the pilot hole 108 is completed. Then, the pilot head 105a is removed. Then, a reamer apparatus provided with a reamer (a diameter enlarging device) is fit, which reamer has a diameter approximately identical with or slightly larger than a pipe diameter of the buried pipe 104.
A conventionally known reamer of a reamer apparatus was a conical one, of so-called spindle type, that corresponds to pebbles and gravel-containing soil (see, for example, JP-A 9-195678(1997) (Pages 3 to 5, FIG. 1)). In this case, a reamer 109 of a reamer apparatus is connected to a rod 105 by being screwed to the rod 105 as shown in FIG. 11, and the reamer 109 is connected to the buried pipe 104 through a coupling member 110. More particularly, a coupling tool 112 is connected to a coupling piece 111 at a rear end of the reamer whereupon the reamer 109 is coupled with a ground drawing jig 113, and a coupling tool 116 is connected to a coupling piece 115 that is provided at a tip end of a welding cup 114 whereupon the ground drawing jig 113 is connected to the welding cup 114 and the welding cup 114 is welded with the buried pipe 104.
Thus, after fitting the reamer apparatus between the hollow road 105 and the buried pipe 104, the hollow rod 105 is retracted into a direction of an arrow B2 shown in FIG. 11 while rotating the hollow rod 105 by means of the drill driving device 102. The earth and sand generated in this time is discharged from a space between the pilot hole 108 and an outer diameter of the rod by emitting the drilling fluid. In addition, a part of the drilling fluid of the reamer apparatus comes round to a rear side to carry out a roll of a lubricant for the buried pipe 104. Then, the cut earth is confined in an inner wall of a hole at an outer periphery of the reamer 109 by rotation with respect to the pilot hole 108 and retracting of the reamer 109, and thereby, the diameter of the pilot hole 108 is enlarged and the buried pipe 104 is retracted in the enlarged hole to be formed along the direction of the arrow B1. Thus, the above-described drilling fluid is used for discharging the drilled earth and sand, lubrication and cooling of the oblique leading body (pilot head) 105a or the reamer 109, and smooth promotion of the rod 105, and further, the bentonite fluid is used for preventing the earth and sand from falling in a drilled hole and improving a pressure density for the wall of the drilled hole.
Then, when the hollow rod 105 is retracted till the front end of the buried pipe 104 protrudes in the starting pit P2, it is possible to set the buried pipe 104 between the attainment pit P3 and the starting pit P2 if the reamer device is detached from the buried pipe 104 and the hollow rod 105 in the starting pit P2. Then, the hollow rod 105 is pulled out from the penetration pit P1. In addition, when the buried pipe 104 is buried for a long distance, the pipe burying operation in the above-described series of processes will be repeated.
In the reamer apparatus of the above publication, the reamer 109 is connected to the buried pipe 104 through a coupling member 110, and a clearance portion (concave portions in the peripheral direction) 117 is formed between the ground drawing jig 113 and a rearward side of the reamer 109. It may therefore happen that sediments that cannot be discharged to the rod side or sediments that are not compressed against the hole inner wall enter this clearance portion 107, and in the presence of such intrusion, the drawing resistance when drawing the buried pipe 104 will become large so that a large drawing force is required. Through such intrusion of sediments to the clearance portion 117, it would happen that an attraction force that is larger than normal drawing force for a buried pipe 104 was required or that the flexibility of the reamer 109 was degraded so that the steerability of drawing of the buried pipe 104 was degraded, and there was the fear that no stable burying operations could be performed. Moreover, there also exists the danger that sediments would intrude and damage a Swivel joint portion, and due to the fact that the used ground drawing jig 113 was of long dimension, the length dimension of the coupling member 110 became accordingly large to thereby degrade the flexibility. Due to the large length dimension of the coupling member 110, the length dimension of a ground aperture hole P2 (reamer connecting hole) became also large so that the degree of so-called overbreak was increased which, in turn, caused increased construction time (operating time).
In FIG. 11, a cover member 118 is provided at the ground drawing jig 113 on the side of the buried pipe, wherein the cover member 118 encompasses a coupling tool 116 for connecting the ground drawing jig 113 and the buried pipe 104, and by providing a similar cover member 120 at the ground drawing jig 113 on the reamer 109 side, it may encompass a coupling tool 112 that connects the ground drawing jig 113 and the reamer 109. However, since the ground drawing jig 113 needs to be bent with respect to the reamer 109, it is necessary to provide a clearance between the cover member 120 and the reamer 109. At this time, since the driving direction is a direction towards the rod 105, sediments will intrude from between this clearance, wherein such sediments were hardly discharged after once intruding into the clearances so that it was feared that the Swivel joint portion was damaged.